Preparation and evaluation of nonionic amphiphilic phenolic biocides in urethane hydrogels
Phenols are rarely used in the preparation of polyurethanes because of the inherent competitive reaction of the phenolic moiety with isocyanates. This work represents a successful application of the combination of phenols with isocyanates toward the development of phenolic-based antimicrobial urethane coatings for niche applications. In this effort, a series of nonionic amphiphilic phenolic molecules were prepared by condensation of 4-hexylresorcinol with the corresponding hydroxyl-terminated monomethyl poly(ethylene glycol) in the presence of a catalytic amount of acid in refluxing toluene. These new molecules were evaluated against a variety of Gram-positive and Gram-negative bacteria for their antimicrobial activity in minimum inhibitory concentration solution testing. The same amphiphilic molecules were also incorporated into a hydrophilic poly-urethane hydrogel and dispensed as films for evaluation of surface activity with a newly developed protocol. All samples possessed some degree of surface antimicrobial activity, which was expressed as a log kill reduction in colony-forming units starting from an initial bacterial concentration of 10(7) CFU, and structural features of the phenolic compound were found to contribute significantly to the observed antimicrobial activity. The highest activity was observed in samples containing the phenolic compound with the shortest ethylene oxide polar structural feature and therefore highest mobility in the highly polar urethane resin. (c) 2007 Wiley Periodicals, Inc.